This invention relates to hermetic type compressors for use in household coolers and refrigerators. More particularly, the invention relates to a hermetic type compressor wherein the cylinder of a compressor unit enclosed in a casing is secured or fixed to the casing by welding, and also to a method for welding the cylinder to the casing.
Hermetic type compressors wherein a compressor unit and an electric motor for driving the same are enclosed entirely in a casing are widely known. The compressor unit is ordinarily of a rotary type comprising a cylinder, a roller rotatable within the cylinder, and a blade which is urged against the peripheral surface of the roller for dividing the internal space of the cylinder into a suction chamber and a compression chamber. When assembling the above described hermetic type compressor, the cylinder of the compressor unit is inserted into the casing in a light force fit manner, and secured to the casing by welding carried out from outside of the casing.
Such a procedure, however, has been found to be disadvantageous in that a welding machine of a large capacity is required because of the comparatively thick casing through which welding is required to be carried out from outside, and that the heat created by the welding, which is inevitably of a considerable amount, tends to deform the outer casing and the cylinder of the compressor unit inclusive of a groove for receiving the blade, thus rendering the operation of the compressor unit unstable and unreliable.
For obviating the above described difficulties, there has been proposed another arrangement wherein a number of through holes are provided beforehand at positions where the cylinder of the compressor unit is desired to be secured to the outer casing by weldings and welding is carried out from the outside of the casing through these holes.
In this case, although the heat created by welding can be substantially reduced, flashes or burrs (or projections) formed between the inner surface of the casing and the outer surface of the cylinder, around these holes, inevitably form an irregular gap between the casing and the cylinder, thereby causing misalignment of the cylinder or an uneven air gap in the electric motor. Furthermore, lack of weld metal in the holes frequently produces void or leakage paths through these holes.